Instead of building towers and defending against hordes of monsters, play the opposite as an evil mage that builds his army from the ground up to dominate the lands.
Build structures, train army, destroy enemy castles. Your soldiers will charge and break through enemy defense lines automatically and use magic to assist your corps assaults.
When scientists discovered a distant, naturally rich planet called the 'Bluegreen Planet', each planet sends their troops to battle for control over it. Train soldiers and build military units and structures to overpower your opponents.